Russia's government unexpectedly resigned on Wednesday after President Vladimir Putin proposed sweeping constitutional changes that could allow him to extend his rule.

Prime Minister Dmitry Medvedev said he was stepping down to give Putin room to carry out the changes, which, if implemented, would shift power to parliament and the prime minister - and might thus allow Putin, 67, to rule on in another capacity after his current term ends in 2024.

Medvedev, a long-time Putin ally and former president, announced his resignation on state TV sitting next to Putin, who thanked him for his work.

As a replacement for Medvedev as Russia's prime minister, Putin on Wednesday evening appointed Mikhail V. Mishustin, a little known bureaucrat who has served for the past decade as head of the Federal Tax Service.

Putin said Medvedev would take on a new job as deputy head of Russia's Security Council, which Putin chairs.

These changes will be seen by many as the start of Putin's preparations for his own political future when he leaves the presidency in 2024, when his fourth presidential term ends.

He has not yet said what he plans to do when his term expires but, under the current constitution, which sets a maximum of two successive terms, Putin is barred from immediately running again.